Author Topic: Flooded Battery Bank Wiring Design  (Read 3795 times)

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Phantom30

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Flooded Battery Bank Wiring Design
« on: April 19, 2015, 01:09:47 PM »
DIY battery bank:  Have questions about cable length issues and impact on equalizing batteries and charging.  Also do connectors have to match battery post and bus bar bolt size?  Have two bus bar driven wiring designs and would like advice on which is the better construct for a battery bank.

joestue

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Re: Flooded Battery Bank Wiring Design
« Reply #1 on: April 19, 2015, 04:19:24 PM »
Estimate the battery impedance to be such that at short circuit, you will get 30 to 40 times the amp hours, in amps.
As such, this means that a 100 amp hour battery will dump 3000 to 4000 amps.
This means its impedance is 2 volts/4000 amps or one half milliohm per cell. or 3 milliohms for a 12v battery, 12 milliohms for a 48 volt battery.

When you connect batteries in parallel, if some batteries and their connection leads have lower resistance than others they will pass more current according to the difference in resistance.

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Phantom30

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Re: Flooded Battery Bank Wiring Design
« Reply #2 on: April 20, 2015, 08:25:02 AM »
So if I translate what you have said, then as long as the total resistance long the path to and from the bus bar is equal for all batteries, then the current well be distributed equally.  So in my designs the central bus is better because all the path lengths are equal.  Thanks.  What about the eyelet sizes do they have to match the stud on the bus bar and battery post or can you use a 3/8" eyelet on a 5/16" stud without concern.

Mary B

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Re: Flooded Battery Bank Wiring Design
« Reply #3 on: April 20, 2015, 06:12:28 PM »
Long as you use a fender washer to distribute surface contact area I see no issue with a 3/8 terminal on a 5/16th stud.

joestue

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Re: Flooded Battery Bank Wiring Design
« Reply #4 on: April 20, 2015, 08:12:07 PM »
4 awg wire makes a 12-28 copper stud/bolt/whatever for far less than you could buy brass or copper hardware btw...

connection resistance is usually somewhere between negligible and 10%.
usually its a connection reliability problem..
My wife says I'm not just a different colored rubik's cube, i am a rubik's knot in a cage.